This invention pertains to an audio amplifier, and in particular to an audio amplifier employing a microchannel plate (MCP).
Audio amplifiers using vacuum tubes have a characteristic sound which musicians and audiophiles find pleasing. In vacuum tube amplifiers, the input signal becomes distorted, especially when the input is overdriven. The distortion seems to result from clipping and rounding of the input waveform so that the resulting sound is softened. Solid state audio amplifiers do not amplify signals in the same way as tubes and thus do not exhibit the distinctive tube sound. Indeed, solid state devices produce a clean signal which to some sounds unpleasing, sharp and harsh. This seems to be the result of sharp clipping when the amplifier is overdriven.
The availability of high quality tubes for audio amplifiers is limited. Some foreign sources produce relatively inexpensive tubes which do not meet the requirements for high end equipment. Such tubes do not have sufficient consistency to be useful as matched pairs in push/pull amplifier configurations.
Domestically manufactured high quality tubes can be found, but such tubes are expensive. There is even a fairly active market in so called new old stock and used tubes. However, the availability of such tubes from a bygone era is limited.
Despite their inferior performance, transistors are popular because they are less expensive to manufacture and to operate, and they are more robust than tubes. Also, tubes require a hot filament to heat the cathode which consumes substantial energy and is a source of tube failure.
It is also difficult and expensive to build multiple channel tube amplifiers.
It is therefore desirable to provide an audio amplifier which mimics the tube sound and which is robust and has a reasonable cost. It is also desirable to provide equipment which will economically handle multiple channels using a common multichannel tube.